The present invention relates to a driving lane recognition system for recognizing a driving lane of a vehicle by executing image processing of a road-surface image taken by a camera, and particularly to a driving lane recognition system for driving in a lane appropriately corresponding with a plurality of lane marker shapes (kinds).
A technology of recognition of vehicle driving lane is a technology necessary for a lane departure warning system of a vehicle, a lane keeping support system for executing steering assist control and so on. In regard to the driving lane recognition technology, there are a method that lane markers formed of magnet are embedded in a load to recognize a driving lane from the magnetic field positions; a method that a position of a vehicle is measured with high accuracy using a differential GPS or a kinematic GPS to calculate a driving lane from highly accurate road map data; and so on. However, any of these methods requires construction of the infrastructure, and accordingly the applicable area is limited.
On the other hand, a method of using image processing by detecting a driving lane from a camera image has an advantage in that the applicable area is wide because there is no need to construct the infrastructure.
In the lane recognition using the image processing, stable recognition is always required in taking various statuses of road surface into consideration. In Japanese Patent Application Laid-Open No.7-128059 disclosing a method in which a parameter or a threshold is changed corresponding to a road surface status, it is described that the threshold used for extracting an edge of a white line of lane maker is determined from the edge intensity. Further, in Japanese Patent Application Laid-Open No. 6-341821, it is described that recognition area is changed by independently setting thresholds from the edge intensities of right and left white lines. As described above, by changing a threshold or a parameter corresponding to a road surface status, stable recognition results can be obtained for various road surface statuses.
Although the conventional technologies cope with the various statuses of road surface by changing the threshold or the parameter, the recognition is made using the image processing algorithm which is created on the premise that the lane markers are white lines.
Most of the lane markers are white lines (yellow lines) in Japan, but raised pavement markers and post cones in addition to the white lines are used as the lane markers in various foreign countries. The detection of driving lane is performed in order to obtain a displacement of a vehicle and a curvature of the lane. When various kinds of the lane markers such as the white line, the raised pavement marker, the post cone and so on are image-processed using a common image processing algorithm, there is a problem in that the recognition accuracy of the resultant recognition rate is degraded.